Myriad devices have been invented to assist golfers in improving the mechanics of their swing. One category of device employs a marker attached to the head of a golf club in combination with a sheet or mat to record the marks generated by swinging the club.
Swords—U.S. Pat. No. 3,687,459 discloses a pair of spaced apart scribers (pens) attached to the head of a club. The tracks of the scribers on a sheet indicate the nature of the golfer's swing.
Golden—U.S. Pat. No. 3,992,013 discloses a dust covered mat and a golf club, modified by attaching a device with protruding pegs to the club head. The attachment is capable of dispersing the dust, when the club contacts the mat.
Blaisdell—U.S. Pat. No. 4,932,662 discloses a club lie angle evaluator having a club whose lower surface has received an abradable coating. When the golf club comes into contact with the surface supporting the golf ball, the coating is abraded, indicating whether the lie angle of the club is appropriate for the particular golfer.
Cerami—U.S. Pat. No. 5,120,064 discloses a spring loaded marker attached to the head of a golf club. The marker traces lines on a sheet, indicating the path of the golf club.
Hsu—U.S. Pat. No. 5,620,376 discloses a marker attached to the shaft of a golf club, adjacent the club head. The marker has a chamber for holding a liquid and an orifice at the bottom. Swinging the club releases the liquid and creates a mark on the ground indicating the path of the golf club.
Another category of devices provide a removable recording medium attached to the face of a golf club. When a golf ball is struck, an impression is created in the medium. Examples of such devices are disclosed in Lee—U.S. Pat. No. 5,142,309 and Butler, Jr. —U.S. Pat. No. 5,609,530.
Yet another category of golf swing analysis aids include mats that indicate the swing path of a golf club.
Goduto—U.S. Pat. No. 3,815,923 discloses mats having fibers that are moved from a first position to a second position after being struck by the head of a golf club. The fibers are bicolored, so that the path of the club head will be readily apparent.
Tiffin—U.S. Pat. No. 6,913,544 B2 discloses a divot practice mat having a mark retaining surface, such as carbon paper or wax. Simulated golf balls are imprinted on the surface of the mat and provide a target for the golfer.
Snopkowski—US 2006/0128493 A1 discloses a synthetic turf practice mat having fibers that change visually in appearance after being struck with the head of a golf club. Alternatively, the mat may employ liquid applied to the fibers, sand, aluminum powder or magnetic powder, to visually identify the path of a club head.
Nusbaum et al. —US 2007/0298895 A1 disclose a golf swing analysis mat that has electronic sensors to detect the point of impact and path of a golf club head. A microcontroller analyzes the data and provides feedback to the golfer.
Mitchell—US 2008/0200277 A1 discloses a golf mat with grass-like blades that “toggle” from a forward face to a rearward face, after being struck by the head of a golf club. When the blades are toggled, they appear a different color.